The invention concerns a system detecting so-called flats and weld-ons on rail-equipment wheels.
Frequently, damages to the wheeltreads of rail-bound vehicles result in rolling irregularities. Such damages are among the following:
flat areas caused by material defects, material ruptures, by grinding from fixed brakes, or
accumulations of material (so-called weld-ons), on account of brakes dragging for length of time in the form of brake-shoe material building up on the wheel circumference, and/or abrasion of the wheel.
The resulting running irregularities of the wheels rolling on the rail can directly or indirectly hamper railway operation. Illustratively, the axle bearing may be damaged by the acceleration loads periodically recurring at the same place. Further, there may be rail breakage, especially at lower temperatures. But in every case, such running irregularities cause noise pollution of the environment. All these effects directly affect the economy of railway operation because of the required repairs or steps (noise).
In the past, therefore, a variety of testing steps have been considered and, in part, have even been put to practice to detect flats according to size on a very specific wheel, while, however, being associated with at least the bogie. Illustratively, the state of the art analyzes the amplitudes of high-frequency (hf) track circuits when passed over by a wheel with a flat, the measured effect being a change in resistance between the two rails of one track when the wheel "skips". The test pickups illustratively are strain gauges, which are fastened to the rails and change in resistance when the rail bends horizontally by the impact of a flat. Again, the impact of a flat on the rail can be measured by a piezo-accelerometer mounted on it.
Common to all these devices is that their sensitivity along a rail segment is highly non-linear (hf track circuit) or that the pickup is sensitive only in a very narrow range near its mounting (several cm to each side) along the rail. This fact is based on the physics of detection and much restricts reliable sensing or even classification of the wheel-damage, the damaged site being located randomly on the wheel circumference, and therefore, there is no relation between the impact point and the sensor position at the rail. The state of the art, accordingly, uses very costly analytical algorithms to achieve some linearity in the test result (for instance, in the hf track circuit), or by installing rows of sensors with adjoining or overlapping ranges of sensitivity along the rails. Again, this is not a satisfactory method in the light of the costly installation, the more than trivial sensor costs and the analytical equipment required for a plurality of sensors. This is especially the case for the strain gauges and locally responding accelerometers.